1. Field of the Invention
The present invention generally relates to semiconductor manufacturing processes and more particularly to silicon semiconductor or nano-machine device manufacturing processes.
2. Background Description
Semiconductor manufacturing processes are complex multi-step processes during which compressive or tensile stresses are formed in crystalline structure of the semiconductor wafers or substrates. Often, crystalline dislocations form in the substrate to relieve these high stresses. These crystalline dislocations can cause junction leakage, enhanced diffusion, metal precipitation sites, and other undesirable effects.
Junction leakage can severely reduce dynamic random access memory (DRAM) retention time. Enhanced diffusion causes what is referred to as bipolar pipes. Metal precipitation sites cause shorted junctions.
U.S. Pat. No. 5,441,901 to Candelaria entitled "Carbon Incorporation in a Bipolar Base for Bandgap Modification" teaches the use of carbon in the base region of a bipolar transistor for the purpose of bandgap modification for improved bipolar device performance. Carbon has been combined with typical semiconductor dopants such as Boron, Phosphorous, Arsenic, etc., and co-implanted in silicon to minimize transient enhanced diffusion (TED) that might otherwise occur upon post implantation annealing. Also, carbon has been combined with these dopants to minimize the formation of end-of-range (EOR) implant dislocations at post implantation annealing.
Co-implantation of carbon in these instances is to prevent implant related dislocation damage, as well as transient enhanced diffusion due to the creation of silicon self-interstitials by the implantation of the dopant species (as well as the carbon itself). The presence of the carbon causes the rapid extinction of the silicon self-interstitials upon recrystallization annealing, thereby preventing the formation of end-of-range dislocations, as well as, transient enhanced diffusion of the implanted dopant species.
FIG. 1 shows dislocations at the corners of oxide filled shallow trenches. These dislocations are due to compressive stresses in the oxide filled trenches that act on the surrounding silicon crystal lattice (external forces). SiO.sub.2 compressive stress creates forces on surrounding silicon causing the creation of dislocations (d) at recessed oxide corners.
Deep carbon implants have been used to act as gettering sites for heavy metal contaminants in semiconductors. Substitutional carbon has been introduced into bipolar and FET SiGe regions to inhibit the formation of dislocations due to crystal lattice stresses. These crystal lattice stresses are caused by the incorporation of substitutional germanium into the silicon crystal lattice. Germanium, unlike carbon, is a larger atom than silicon and, when substituted for silicon in the crystal lattice at a sufficient concentration, it creates compressive stresses that can cause dislocation formation. Substitutional carbon has been included in these devices to relieve intrinsic stresses so as to prevent dislocation formation.
Thus, there is a need for reducing or eliminating external stress to prevent dislocation formation.